Internal combustion engine system



Oct. 22, 1968 T. H, OSTER 3,406,673

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THOMAS h. 05 7' ER United States Patent 3,406,673 INTERNAL COMBUSTIONENGINE SYSTEM Thomas H. Oster, Deal-born, Mich., assignor to Ford MotorCompany, Dearborn, Mich., a corporation of Delaware Filed Dec. 30, 1966,Ser. No. 606,370 2 Claims. (Cl. 123-169) ABSTRACT OF THE DISCLOSURE Thisinvention is concerned with an internal combustion engine containing aspark plug with an aurous electrode and an electrical system which isincapable of generating a spark impulse higher than that required by theaurous spark plug.

Background of the invention This invention relates to the combination ofa conventional internal combustion system with an aurous spark plug andan electrical system especially designed to incorporate the economiesmade possible by the unique characteristics of the aurous spark plug.

The use of spark plugs in conventional internal combustion engines istoo well known to require further elaboration. Judicial notice may betaken of the fact that the ignition system in general and the sparkplugs in particular are the Achilles heel of modern engines. A new sparkplug with sharp clean electrodes and a properly spaced gap will firereadily and reliably with a moderate voltage. However, spark plugsrapidly deteriorate in normal use. The action of the spark tends toerode the metal of the electrodes thereby rounding ofi sharp edges whichinherently produce a high electrostatic gradient and ready ionization ofthe adjacent air prior to conduction. The same erosion of the metalelectrodes increases the gap which must be jumped by the spark. Each ofthese changes increases the voltage which must be available to the sparkplug it the engine is to fire properly. This increase in voltageincreases harmfully the energy dissipated in the spark gap.

This combination of circumstances has compelled the use of sparkproducing electrical apparatus capable of much higher voltages thanwould be required by new spark plugs so that a reasonable spark pluglife can be attained. This expedient is to some extent self defeating asthe energy expended in the spark gap increases with increasing voltagethereby increasing the rate of metal erosion and leading to ultimatefailure of the spark plug. This failure often occurs when the foulingdeposits of carbon and lead salts which are inevitably present provideashunt path for the sparking current which efiectively prevents sparkingwhen the voltage at the spark plug must be elevated to jump theincreased gap with rounded electrodes.

Summary This invention is predicated upon the fact that gold is the onlyknown metal which appears to be completely stable in the metallic state.The substitution of a gold electrode for one of the electrodes in aconventional spark plug appears to halt almost completely the erosiveeffects mentioned above which tend to round off electrode edges and toincrease the spark gap. Even more surprising only one of the electrodesneed 'be fabricated from aurous material. The other electrode may be thefamiliar nickel base alloys long used as electrodes in spark plugs.

The aurous electrodes need not be pure or fine gold, but may well bealloyed with other metals which tend to decrease the volatility of goldor to raise its melting point. Chromium and palladium are examples oftwo such 3,406,673 Patented Oct. 22, 1968 metals which may be alloyedwith the gold. The gold content should be retained sufiicie'ntly highthat the peculiar and unique oxidation resistant quality of gold is notsubstantially impaired. At least one portion of the aurous electrodeshould have a sharp edge to decrease the potential necessary to producea spark. The aurous electrode should be supported in intimate thermalcontact with a base metal heat sink of sufficient mass and thermalconductivity to prevent undue temperature elevation of the gold.

The use of an aurous electrode in an otherwise conventional spark plugprevents the elevation of sparking voltage with use which occurs withthe normal base metal electrodes and to a lesser extent with the veryspecial platinum electrode spark plugs. This low and stable sparkingpotential renders it possible to redesign the electrical system for theproduction of the sparking impulses so that it is incapable ofgenerating voltages substantially higher than are necessary to fireplugs in the new condition. This makes possible a more economicalelectrical system to build and one which is more reliable in use. Theinsulation problems throughout the entire sparking system are far lesssevere and the current carrying capacity of the contact points may bereduced. Similarly, less difiiculty is encountered with very high enginespeeds since the energy necessary to adequately charge the spark coil isless.

Brief description of the drawing The sole figure of drawing is agraphical representation of the voltage at a spark plug necessary tofire the spark plug reliably under a variety of conditions. These testswere conducted with the base metal electrodes and with a spark gap of0.030 in. The dotted curve labeled Transient Load Voltage defines thevoltage necessary to reliably fire a spark plug when the throttle issuddenly opened wide. It is this voltage which is meant in the appendedclaim by the language that required to ionize the gas between theelectrodes under conditions of maximum pressure in the compressionchamber.

The space between this dotted curve and the upper curve which islabelled Available Voltage represents voltage ability which need not bebuilt into the system when aurous electrodes are employed.

Description of preferred embodiment The particular spark plug structurewhich makes possible the construction claimed herein is produced byaltering the construction of the center wire of an otherwiseconventional spark plug. The final one quarter to one half inch of thecenter electrode wire is made by welding securely to the inconelremainder of the center wire a gold wire approximately one sixteenth ofan inch in diameter and terminating in a square end. The gap between thesquared end of the center wire and the other electrode is set at about0.030 inch. In such a system, the remainder of the electrical systememployed to energize this spark gap may safely be limited to not over12,000 volts. The actual energy available at the spark gap may well belimited to not over one millijoule and can usually be limited to halfthis value by virtue of the fixed aurous spark gap.

I claim as my invention:

1. An internal combusion engine comprising a piston, a compressionchamber adjacent the end ofthe piston stroke, means for moving thepiston towards the compression chamber to adiabatically compress airinto the compression chamber and thereby increase the resistance of suchair to ionization, a spark plug in communication with the compressionchamber and an electrical system for energizing the spark plug, saidspark plug including a pair of gap'ped sparking electrodes one of whichis fabricated from fine gold or an alloy of fine gold with an amount ofnon-gold metallic substances in an amount to enhance the resistance offine gold to melting and evaporation but insufficient to substantiallylessen the resistance of fine gold to oxidation under the conditionsexisting in the compression chamber, said gold electrode including atleast one edge of small radius to increase locally the electrostaticgradient tending to ionize the adjacent air, said gold electrode beingsupported'in intimate thermal contact with a thermal sink of sufficientmass and thermal conductivity to limit the temperature reached by thegold electrode, said electrical system including a source of highvoltage comprising an iron core and an electrical coil surrounding theiron core and generating a high voltage impulse by a rapid change in themagnetic flux existing in the iron core, said electrical system beingcharacterized by the fact that the energy dissipated in the gap between4. the sparking electordes increases rapidly as the length of the gapincreases and beingfurther characterized by the fact that the systemproviding the high voltage is electrically incapable of generating anelectromotive force substantially in excess of that required to ionizethe gas between the electrodes under conditions of maximum pressure inthe compression chamber. a l

2. The system recited in claim 1 in which the actual electrical energydissipated in the spark gap is limited to a value not materially-inexcess of one millijoule.

References Cited UNITED STATES PATENTS' 1,561,247 11/ 1925 Kings'bury75-165 1,565,358 12/1925 Gardner 75165 2,326,028 8/ 1943 GriifithsLAURENCE M. GOODRIDGE, Primary Examiner.

